Vehicle suspension system



April 19, 1966 H. J. KOZlCKl 3,

VEHICLE SUSPENSION SYSTEM Original Filed June 25, 1963 2 Sheets-Sheet lHf/VA) I AOZ/CK/ I NVENTOR.

42 MAMA April 19, 1966 H. J. KOZICKI 3,246,718

VEHICLE SUSPENSION SYSTEM Original Filed June 25, 1963 2 Sheets-Sheet 2///V/?) J KOZ/CK/ INVENTOR.

WM 12. Awe/a WW 1% mm A T TOP/V675 United States Patent C) 7 Claims. or.180--73) This invention relates generally to vehicle suspension systemsand more particularly, to a suspension having means adapted to maintainthe vehicle at a level attitude with respect to the ground regardless ofchanges in vehicle loading.

An examination of the prior art relating to vehicle sus pension systemswill disclose a large number of devices that are designed to compensatefor changes in vehicle loading. In passenger cars having soft springing,devices that will return a vehicle to a level attitude upon the additionof passengers, luggage or other loads have been found to be highlydesirable. A majority of these systems employ auxiliary springs,inaddition to the main suspension springs, to support a portion of thevehicle sprung weight. To provide a load leveling or load compensatingfunction, a mechanical actuating device is associated with the auxiliarysprings and is adapted to increase or decrease the load carried by thosesprings in response to an increase or decrease of the loading upon thevehicle. It is customary in such systems to have the mechanicalactuating device sensitive to car height and responsive to changesthereof in order to perform its leveling function.

Thus, in these conventional systems a regular suspension is provided forsupporting the chassis and, in addition, an actuatable auxiliarysuspension is provided to make height adjustments.

In accordance with the present invention, however, a vehicle suspensionsystem is provided having compensating means to maintain a vehicle at aconstant height without the use of auxiliary springs in the event of achange in sprung weight. More specifically, changes in vehicle loadingare compensated for by making changes in the geometrical arrangement ofthe suspension linkage. In the conventional rear suspension systemhaving a solid driving axle and a pair of coil springs, trailing armsare usually provided to position the axle. It has been discovered thatthe geometrical relationship between the various arms or'links may beadjusted so as to change the efiective forces exerted by the suspensionsprings in supporting the sprung weight; If adjustment means areprovided as contemplated by the present invention, geometrical changesmay be made that will alter the distribution of forces and the vehiclemay be' returned to its designed height after a change in loading.

It is one of the principal objects of the present invention, therefore,to provide a vehicle suspension system in which vehicle height ismaintained at a designed level by alterations in the geometry of thesuspension and without the employment of auxiliary spring devices.

More specifically, it is an object of the present invention to providean embodiment in a vehicle having a solid rear axle and a pair of lowertrailing arms joining the axle with the vehicle chassis. An upper armconnects the axle with the chassis and suspension springs are interposedbetween the lower arms and the chassis. An adjustable pivotal connectionis interposed where the upper arm is connected to the chassis so thatthe angular relationship between the upper and lower arms may be readilymodified to accommodate load changes.

The many objects and advantages of the present invenice tion will becomeapparent from the following description and the accompanying drawings inwhich:

FIGURE 1 is a schematic side elevational view of a vehicle rearsuspension incorporating an embodiment of the present invention;

FIGURE 2 is an elevational view corresponding to FIGURE 1 with ageometrical analysis of the suspension linkage;

FIGURE 3 is a schematic view corresponding to FIG- URE 2 of an alternateconstruction of the present inventron;

FIGURE 4 is a schematic view corresponding to FIG- URE 2 of a stillfurther modification of this invention;

FIGURE 5 is a top plan view of a rear suspension system incorporatingthe embodiment of the invention illustrated in FIGURES 1 and 2; and,

FIGURE 6 is a side elevational view of the actuator portion of thesuspension of FIGURE 5.

For a better understanding of the present invention, reference is nowmade to the drawings wherein like reference numerals identify like partsthroughout the various views. In FIGURE 1, a wheel 10 resting upon theground line 12. is disclosed. The wheel 10 is rotatably connected to anaxle housing 14. A bracket 16' extends downwardly and forwardly of theaxle iii and is pivotally connected to a lower suspension arm 18'. Theforward end of the lower arm 18 is pivotally connected to a support 20carried by the chassis or sprung mass of the vehicle. A coil typesuspension spring 22 is disposed between a midpoint on the arm 18 and aspring seat 24 of the chassis.

A bracket 26 extends upwardly from the axle housing 14 and is pivo-tallyconnected to an upper suspension arm 28. Upper arm 28 extends forwardlyfrom the bracket 26 and has a pivotal connection 29 with a chassismounted support member 32. The support member 32 is adapted to readilymove the location of pivot 29 so that the inclination of the arm 28relative to the lower arm 18 may be varied.

This invention accomplishes the leveling of a vehicle after a load isadded or removed by means of a geometrical change in the suspensionlinkage rather than by the loading or unloading of a leveling orauxiliary spring as in a conventional leveling type suspension system.An understanding of the present invention and its theory of operationcan be obtained from an analysis of the forces which act upon the arms,the wheel, the axle housing, and the various pivots.

In FIGURE 1, the vehicles weight is indicated by the arrow W. Arrow W ispointing upwardly as it represents the ground reaction. The spring 22,carrying the sprung weight of the vehicle, exerts a force F upon thepivotal connection 17 between the lower arm 18 and bracket 16. Force Fdoes not equal force W because there is also an upward force F upon theaxle due to the inclination of the upper arm 28. Force F results fromthe fact that forces F and W act across the distance d, and thus createa couple that tends to make the axle housing 14 rotate in acounterclockwise manner as viewed in FIG- URE 1. This couple is resistedby a clockwise" couple consisting of the forces indicated by arrows Facting across the distance d The arm 28 is freely pivoted at its endsand, therefore, can carry forces that act only along its longitudinalaxis. For that reason, force F is the horizontal component of force Fwhich is parallel to the axis of the upper arm 28. Force F also has avertical component F situated at the pivotal connection 19 between thebracket 26 and the arm 28. A corresponding reaction force F also appearsat the inner pivot 29 where the arm 28 connects with the support 32.

It is, therefore, evident by summation of vertical forces (which mustbalance) that force F equals force W plus force F According to theaction-reaction principle, force F appears at pivot 29 of the upper arm28 in a direction tending to push the vehicle chassis down. The springforce F is greater than the cars actual weight by an amount equal toforce F If the loading of the vehicle is increased, the vehicle chassiswill descend. In order to level the vehicle, the inclination of theupper link or arm 28 is shifted by mechanical means to the positionindicated generally as 28. If the arm 28 were in the horizontal position28, as shown in the drawing, there would be no downward force F on thevehicle and force F would be equal to the new weight W. With the arm 28horizontal, force F; would become force F and there would be no verticalcomponent F The added load, in other words, took the place of theprevious downward force P with the result that the vehicle remains atthe same height.

If the car had been made lighter by removing some of its load, thedownward force F could be increased to compensate for the load change byincreasing the inclination of the upper arm 28 to the position 28". Theresult would be restoration of the vehicles level attitude.

In either case, it is contemplated that the inclination of arm 28 willbe changed sufficiently to effect an increase or decrease in themagnitude of force F equal to the change in vehicle loading that isbeing compensated for.

One mechanical means for positioning the inner pivot 29 of the upper arm28 in order to effect proper arm inclination for vehicle levelingpurposes is illustrated in FIGURES 5 and 6 and will be described later.

The theory of this invention can also be proven by the concept ofinstantaneous centers as shown in FIGURE 2. It can be shown that point Ais the instantaneous center of the lower arm 18 and the upper arm 28when the vehicle is at its designed height and carrying its designedload. (Point A is the imaginary point where the axes of arms 18 and 28intersect.) According to the theory of instantaneous centers, the carweight W multiplied by its lever arm L must equal the force F times itslever arm L Expressed mathematically, the formula is F (L )=F (L Bothlever arms L and L are measured from the instantaneous center A.

To accommodate a change in load W, the relationship of L and L isadjusted by means. of repositioning the inner pivot 29 in order toestablish a new instantaneous center.

In the event the vehicle should have an increase in load, pivot 29 israised so that the axes of the upper and lower arms 28 and 18 intersectat a new instantaneous center A. By establishing the new instantaneouscenter A, the ratio of the lengths of lever arms L and L through whichthe forces F and W act is changed so as to compensate for the increasein the vehicles load or force W.

Instantaneous center A" represents the inclination of the upper arm 28to compensate for a decrease in vehicle loading. If the vehicle ofFIGURE 2 has its load removed, then the suspension geometry must bechanged to return it to its designed height. This is done by increasingthe inclination of the upper arm 28 so that its axis intersects the axisof the lower arm 18 at an instantaneous center A. Under thesecircumstances, the force F will be operating through a shorter lever armlength L to compensate for the decrease in the force W times its shorterlever arm L FIGURES 3 and 4 show alternate forms of the invention. InFIGURE 3, the axle housing bracket connected to the lower arm 118extends downwardly and rearwardly as indicated by reference numeral 116.With this arrangement, the force F is situated behind the axle 14. Thesame relationship of forces [F(L )=W(L occurs with this constructionexcept that the force in the upper arm 28 becomes a tensile load insteadof a compressive load as in FIGURES 1 and 2. Point A represents theinstantaneous center of the upper arm 28 and the lower arm 118 atdesigned loading. Point A indicates the necessary position of the upperarm 28 in order to obtain the proper instantaneous center for returningthe vehicle to a level attitude when it is under a heavily loadedcondition.

Instantaneous center A corresponds to the inclination of the upper arm28 when the vehicle carries less than its designed load. In FIGURE 3,distances L and L indicate the lever arm lengths through which theforces F and W operate when the vehicle is in such an unloadedcondition.

The basic idea behind the invention illustrated in FIGURES 2 and 3 isthe alteration of the ratio between the lengths L and L by therelocation of the instantaneous center. In these embodiments, the changeis effected by changing the inclination of the upper arm 28 by movingits forward pivot. The shift of the instantaneous center might also beaccomplished by adjusting the inclination of the lower arm 218 as shownin FIGURE 4. In fact, both arms may be changed simultaneously if this isdesired. As in the embodiments of FIGURES 2 and 3, point A of FIGURE 4indicates the necessary instantaneous center for a loaded condition andpoint A indicates the necessary instantaneous center for an unloadedcondition. By shifting the inner pivot of the lower arm 218 to theloaded and unloaded positions 218' and 218", respectively, a balance offorces and lever arm lengths may be achieved to maintain the vehicle atits designed height.

FIGURES 5 and 6 illustrate one possible mechanical arrangement forperforming the invention illustrated in FIGURES 1 and 2. A similararrangement would also be appropriate for the embodiments of FIGURES 3and 4. In FIGURE 5, the rear wheels 10 are separated by an axle housing14 which carries left and right lower brackets 16. The lower arms 18extend forwardly from the brackets 16 and are pivotally connected tomounting brackets 20 that are secured to the chassis of the vehicle.Coil springs 22 are shown mounted on the arms 18.

The bracket 26 extends upwardly from the axle housing 14 off-center fromthe differential 30. The upper arm 28 is connected to the bracket 26 andextends forwardly therefrom. The forward end of the upper arm 28 isconnected to one leg of a bell crank 32 by a pivot bolt 29. The bellcrank 32 has its fulcrum 34 pivotally mounted on chassis structure. Thebell crank 32 has its other leg extending downwardly and connected to apower strut 36 interposed between the end of the bell crank 32 and achassis pivot 38.

With the foregoing structure, when the power strut 36 is actuated, thecrank 32 pivots about its fulcrum point 34 causing its connection at 29with the upper arm 28 to be displaced. The strut 36 may be eitherextended to lower the pivot point 29 and thereby increase theinclination of the arm 28 or it may be retracted to decrease theinclination of the arm 28. The strut is retracted to compensate for anincrease in load and extended to compensate for a decrease in load.Reference numeral 28 indicates the axis of the upper arm 28 whenadjusted for an increase in load and reference numeral 28" indicates theposition of the arm for a decrease in load.

A minimum amount of energy is required for the leveling operation. Theenergy stored in the coil spring 22 remains the same for either a heavyload or a light load because the height of the vehicle and consequentlythe length of coil spring 22 remains the same. The energy stored in aspring is a function of the spring rate and the amount of its staticdeflection and, therefore, it is apparent that the energy stored in aspring 22 is constant because its rate and amount of static deflectionare constant. The only energy required to level then, is the amountnecessary to break friction in the pivots and the amount needed toaccomplish the physical task of relocating whatever pivots are utilized.

In place of the power strut 36, a cable running forward to a lever ofsome sort that the driver could physically operate would provide amanual leveling system. Since the power requirements are at a minimum ina constant energy suspension, this would require minimum driver effort.

The foregoing description presents the presently preferred embodimentsand theory of operation of this invention. Alterations and modificationsmay occur to those skilled in the art that will come within the scopeand spirit of the following claims.

I claim:

1. A vehicle suspension system having a wheel support member, a vehiclechassis structure, first and second suspension arms interconnecting saidchassis structure and said wheel support member, said first arm havingone end pivotally connected to said wheel support member at a pointdisplaced from the center of said member and another end pivotallyconnected to said chassis structure, a suspension spring interposedbetween one of said arms and said chassis structure, said second armhaving one end pivotally connected to said wheel support member at apoint longitudinally displaced from the pivotal connection of said oneend of said first arm, an intermediate member movably connected to saidchassis structure, said second arm having another end pivotallyconnected to said intermediate member, power actuating means connectedto said intermediate member and connected to said chassis structure andconstructed to move said intermediate member and the other end of saidsecond arm relative to said chassis structure from a first fixed staticposition to a second fixed static position whereby the geometricalrelationship between said two suspension arms is changed.

2. The combination of claim 1 wherein said suspension spring isinterposed between said first arm and said chassis structure.

3. A vehicle suspension system having a wheel support member, a vehiclechassis structure, lower and upper suspension arms interconnecting saidframe and said wheel support member, a suspension spring interposedbetween said lower arm and said chassis frame, said lower and upper armsbeing arranged so that said spring normally imposes a load upon saidupper arm under static conditions, said lower arm having one endpivotally connected to said wheel support member at a point displacedvertically and longitudinally from the center of said wheel supportmember, said lower arm having another end pivotally connected to saidchassis structure, said upper arm being pivotally connected to saidwheel support member at a point vertically displaced from the center ofsaid wheel support member, said just mentioned point also beinglongitudinally and vertically displaced from the pivotal connectionbetween the one end of said lower arm and said wheel support member, anintermediate member movably connected to said chassis frame, said upperarm having another end pivotally connected to said intermediate member,power actuating means connected to said intermediate member andconnected to said chassis frame and constructed to move saidintermediate member and its pivotal connection with said upper arm froma first fixed position to a second fixed position in order to effect achange in the geometrical relationship between said lower and uppersuspension arms whereby the spring load imposed upon said upper arm ischanged.

4. A vehicle suspension system having a wheel support member, a vehiclechassis structure, first and second suspension arms interconnecting saidframe and said wheel support member, a suspension spring interposedbetween said first arm and said chassis frame, said first and secondarms being arranged so that said spring normally imposes a load uponsaid second arm under static conditions, said first arm having one endpivotally connected to said wheel support member at a point displacedvertically and longitudinally from the center of said wheel supportmember, said first arm having another end pivotally connected to saidchassis structure, said second arm being pivotally connected to saidwheel support member at a point vertically displaced from the center ofsaid wheel support member, said just mentioned point also beinglongitudinally and vertically displaced from the pivotal connectionbetween the one end of said first arm and said wheel support member, anintermediate member movably connected to said chassis frame, said secondarm having another end pivotally connected to said intermediate member,power actuating means connected to said intermediate member andconnected to said chassis frame and constructed to move saidintermediate member in its pivotal connection with said second arm froma first fixed position to a second fixed position in order to effect achange in the geometrical relationship between said first and secondsuspension arms whereby the spring load imposed upon said second arm ischanged.

5. A vehicle suspension system having a wheel support member, a vehiclechassis structure, first and second suspension arms interconnecting saidframe and said wheel support member, a suspension spring interposedbetween said first arm and said chassis frame, said first and secondarms being arranged so that said spring normally imposes a load uponsaid second arm under static conditions, said first arm having one endpivotally connected to said wheel support member, said first arm havinganother end pivotally connected to said chassis structure, said secondarm being pivotally connected to said wheel support member at a pointlongitudinally and vertically displaced from the pivotal connectionbetween the one end of said first arm and said wheel support member, anintermediate member movably connected to said chassis frame, said secondarm having another end pivotally connected to said intermediate member,power actuating means connected to said intermediate member andconnected to said chassis frame and constructed to move saidintermediate member and its pivotal connection with said second arm froma first fixed position to a second fixed position in order to effect achange in the geometrical relationship between said first and secondsuspension arms whereby the spring load imposed upon said second arm ischanged.

6. A vehicle suspension system having a wheel support member, a vehiclechassis structure, first and second suspension arms interconnecting saidframe and said wheel support member, a suspension spring interposedbetween one of said arms and said chassis frame, said first and secondarms being arranged so that said spring normally imposes a load upon theother of said arms under static conditions, said first arm having oneend pivotally connected to said wheel support member, said first armhaving another end pivotally connected to said chassis structure, saidsecond arm being pivotally connected to said wheel support member at apoint longitudinally and vertically displaced from the pivotalconnection between the one end of said first arm and said wheel supportmember, an intermediate member movably connected to said chassis frame,said second arm having another end pivotally connected to saidintermediate member, power actuating means connected to saidintermediate member and connected to said chassis frame and constructedto move said intermediate member and its pivotal connection with saidsecond arm from a first fixed position to a second fixed position inorder to effect a change in the geometrical relationship between saidsuspension arms whereby the spring load imposed upon said other arm ischanged.

7. A motor vehicle having a pair of driving wheels, a rigid axle housinginterposed between said wheels and rotatably supporting said wheels, achassis frame, a pair of lower suspension arms each having one endpivotally connected to said frame and the other end pivotally connectedto said axle housing, a suspension spring interposed between each ofsaid arms and said frame, an upper suspension arm pivotally connected atone of its ends to said axle housing by means providing a pivot axisoffset from the center of said axle housing, a power actuatable deviceoperatively interconnecting the other end of said upper arm and saidframe, said device beingconstructed to move said other end of said upperarm along a fixed path from a first static position to a second staticposition with respect to said frame in order to eifect a change in thegeometrical relationship between said upper arm and said lower arms,said lower arms being each pivotally connected to said axle housing by apivot bracket having its pivot support axis displaced downwardly andlongi- References Cited by the Examiner UNITED STATES PATENTS 2,998,2658/1961 Kozicki 280-124 3,163,440 12/1964 Vail 280124 X 3,175,836 3/1965Mather 180-73, X

BENJAMIN HERSH, Primary Examiner.

E. E. PORTER, Assistant Examiner.

7. A MOTOR VEHICLE HAVING A PAIR OF DRIVING WHEELS, A RIGID AXLE HOUSINGINTERPOSED BETWEEN SAID WHEELS AND ROTATABLY SUPPORTING SAID WHEELS, ACHASSIS FRAME, A PAIR OF LOWER SUSPENSION ARMS EACH HAVING ONE ENDPIVOTALLY CONNECTED TO SAID FRAME AND THE OTHER END PIVOTALLY CONNECTEDTO SAID AXLE HOUSING, A SUSPENSION SPRING INTERPOSED BETWEEN EACH OFSAID ARMS AND SAID FRAME, AN UPPER SUSPENSION ARM PIVOTALLY CONNECTED ATONE OF ITS ENDS TO SAID AXLE HOUSING BY MEANS PROVIDING A PIVOT AXISOFFSET FROM THE CENTER OF SAID AXLE HOUSING, A POWER ACTUATABLE DEVICEOPERATIVELY INTERCONNECTING THE OTHER END OF SAID UPPER ARM AND SAIDFRAME, SAID DEVICE BEING CONSTRUCTED TO MOVE SAID OTHER END OF SAIDUPPER ARM ALONG A FIXED PATH FROM A FIRST STATIC POSITION TO A SECONDSTATIC POSITION WITH RESPECT TO SAID FRAME IN ORDER TO EFFECT A CHANGEIN THE GEOMETRICAL RELATIONSHIP BETWEEN SAID UPPER ARM AND SAID LOWERARMS, SAID LOWER ARMS BEING EACH PIVOTALLY CONNECTED TO SAID AXLEHOUSING BY A PIVOT BRACKET HAVING ITS PIVOT SUPPORT AXIS DISPLACEDDOWNWARDLY AND LONGITUDINALLY FROM THE CENTER OF SAID AXLE HOUSING ANDFROM THE CONNECTION BETWEEN SAID UPPER SUSPENSION ARM AND SAID AXLEHOUSING.